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Is it ok to use pipes supported on T-poles as part of the structure itself?

Is it ok to use pipes supported on T-poles as part of the structure itself?

Is it ok to use pipes supported on T-poles as part of the structure itself?

(OP)
There was a previous thread (now closed), "Pipes Resisting Pipe Rack Loads" thread483-345828: Pipes Resisting Pipe Rack Loads, that ran along a similar vein.

Let's say, I have to analyze and design numerous 10-foot high T-pole pipe supports, spaced at say, 20 ft. apart, running along a straight line. All dimensions are arbitrary. The top of the T itself is, say 5 feet wide. This T-pole support is designed to support a 20-inch diameter pipe, that is 100 feet long total. The pipe sits perpendicular to the top of the T. 2 ft long by 5 inches tall steel shoes (visualize an upside down T) are welded to the bottom of the pipes, and the bottom part of the shoe (the bottom part of the upside down T) sits on top of the T-support. The shoes themselves just sit freely on top of the T, and not connected to the steel structure in any way. The pipes are limited in their movements on top of the T support by angles and limit stops.

1. Can you use the pipes supported on these T-supports as part of the structure itself when analyzing and designing this structure? As in, can we assume that the T-supports are braced by the pipes, so that we use a K value of 1.0 for the column (translation fixed), instead of a K value of, say, 2 (translation free)?

2. Can we assume that the story drift at the top of the T-support will not be a factor in our analysis even if the story drift exceeds Code-specified limits, because the T-pole is "braced" by the pipes?

This particular case may be more clear-cut in that the shoes supporting the pipes are not physically connected to the T-supported, and there is only friction acting between the shoe and the top of the T.

3. How about less clear cut situations, where the pipes are physically connected to the T, through being supported on saddles that are actually welded to the T-support? Is this more acceptable as being considered to be "braced" by the pipes?

4. And if, as some have suggested, that they have considered the pipes are part of the structure without any problems, will any problem arise as far as the T-support is concerned if the pipes were to be removed, temporarily or permanently?

RE: Is it ok to use pipes supported on T-poles as part of the structure itself?

1. Normally yes you can assume that the pipes brace the T supports (K=1 for pinned end columns, 0.5 for a moment carrying base plates)

2. Drift forces may eccentrically load the columns and ultimately any drift forces in the pipe axial direction must be resisted by moment carrying base plates or a brace or two between T-supports, say every 100 feet or so.

2.5 You might also take a little credit for pipes restraining drift in the lateral direction too. How much I will leave to you. For wind, or earthquake loads, none, but for other type of loads, some might be considered.

3. Without any weld the limit of restraining force would be the friction force. Welded obviously much higher.

4. Obviously it is highly desirable that any structure be able to withstand its own weight under any load and restraint condition it is likely to encounter during its life time. If you make a T support that needs pipe to stabilize it, then removing the pipe could present a big problem, especially if someone wasn't prepared for the possible results. I'd recommend that they be self supporting under static, light load, erection loads and maybe light wind condition, but perhaps they could be considered pipe-braced for maximum wind and earthquake loads, but I think the economics of that are questionable. Penny wise, pound foolish. Don't outsmart yourself.





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